The UN refugee agency says that over 700 migrants have drowned in Mediterranean Sea shipwrecks south of Italy over the past several days as they tried to reach Europe.

UNHCR spokeswoman Carlotta Sami told the Associated Press news agency that an estimated 100 people are missing from a smugglers' boat, which capsized on May 25.

The Italian navy photographed the horrific ordeal of the capsizing as it rushed to rescue those thrown into the sea.

Another 550 are missing from another boat that capsized on the morning of May 26 after leaving the western Libyan port of Sabratha a day earlier.

Sami says refugees say the boat, which was carrying about 670 people, didn't have an engine and was attached to another smuggling boat before it overturned. Some 25 people survived by swimming to the first boat, 79 others were rescued, and 15 bodies were recovered.

In a third accident on May 27, 45 more bodies were recovered from the shipwreck with many more reported missing.

Italy's southern islands are the main destinations for the smuggling boats carrying migrants from Libya each week.